370 REPRODUCTIVE ORGANS OF MARSILEACEA. 
cases (fig. 816) with four lobes, each of which contains one large 
spore (macrospore) ; but in some cases they are 4-valved. The 
macrospores OY megaspores are in number 2, 4, or 8. 
The antheridia or microsporangia are somewhat reniform two- 
valved cases (jig. 815), containing a large number of small spores 
(microspores), in which antherozoids are ultimately produced. 
The large spores are considered by Hofmeister and others as 
the analogues of the ovules. The antheridia or microsporangia 
are therefore to be considered as the male organs, and the 
macrosporangia as the female. 
In germination, the large spore produces a prothallium in its 
interior, thus resembling the Marsileacez. In this archegonia 
are soon developed, and ultimately a new plant is produced by 
fertilisation taking place by means of the antherozoids. 
An order called Isoétaceze, which includes the species of 
Isoétes, is sometimes placed next to the Selaginellacez. It has 
essentially the same characters, except as regards its nutritive 
organs. ’ 
5. MARSILEACE® OR PEPPERWORTS.—In the plants of this 
order the fructification is placed at the base of the leaf-stalks. 
It consists usually of a two-valved stalked 
Fic. 817. sporocarp (jig. 817, s), which is generally 
many-celled, or sometimes only one-celled. 
The contents of the sporocarps, and the mode 
in which they are arranged, vary, however, in 
the different genera of this order, and hence it 
will be necessary for us to allude to them 
separately. 
In Marsilea, the fructification consists of a 
stalked two-valved hardened sporocarp (jig. 
817, s). The valves are held together by a 
gelatinous ring, which is at first connected 
with the stalk of the sporocarp, but when 
the latter organ bursts, the ring becomes de- 
tached from the stalk at one end, straightens, 
and appears as a long gelatinous cord pro- 
truding from the sporocarp (jig. ml P)s Ne 
; bearing on its sides somewhat oblong spikes 
PG Pats banca of fructification, f. These spikes are at first 
Marsilea, s. Two- enveloped ina membrane, and are composed of 
pee two distinct organs, called antheridia or micro- 
Fructification. sporangia ; and macrosporangia, megasporangia 
or sporangia. These organs are attached to 
a sort of placenta, the antheridia being on one side, and the 
sporangia on the other. 
Each sporangium or female organ contains but one spore, 
called an ovulary spore, macrospore, or megaspore. It consists of 
a central nucleus, surrounded by a cellular coating except at 
its apex, where there is alittle cavity. According to Hofmeister, 
